The FBI has conducted more than 100 investigations into suspected Islamic extremists within the military, NPR has learned. About a dozen of those cases are considered serious.

Officials define that as a case requiring a formal investigation to gather information against suspects who appear to have demonstrated a strong intent to attack military targets. This is the first time the figures have been publicly disclosed.

The FBI and Department of Defense call these cases “insider threats.” They include not just active and reserve military personnel but also individuals who have access to military facilities such as contractors and close family members with dependent ID cards.